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A Level · Cambridge (CIE) · 9990

Hassett et al. · monkey toy preferences

Examine the rhesus-monkey toy-choice study as structured observation in a social group. Separate its observed preferences from the authors’ proposed biological explanation and from claims about children.

Cambridge International AS & A Level Psychology 9990 · 2028–2030 · Version 1 · CORE-02
Exam scope and assessment notes

Original StudyForA teaching mapped to the Cambridge 2028–2030 syllabus. These lessons are independent study support, not Cambridge material, official mark schemes or awarded grades. No lesson reproduces a research article or Cambridge question. Human subject-expert review and full timed-paper grading remain pending. This lesson synthesises the named study from its original article and Cambridge's study outline; it is an original summary, not a reproduction of the paper.

Before you begin

  • This is one of the 12 compulsory AS core studies in the 2028–2030 Version 1 syllabus. Check that your exam entry uses this syllabus year.

Work on paper. Try each question before revealing help, and explain why your method works.

Quick readiness check

What did the observers record?

What you will learn

  • Explain the study aim, sample, procedure and findings
  • Evaluate the method, ethics and evidence
  • Apply the relevant approach and issues/debates without overclaiming

Approach and research focus

Biological approach. The study examines whether male and female rhesus monkeys interact differently with wheeled and plush toys. It asks whether a pattern can occur in a species without human gendered toy marketing or direct human instruction.

Background: Human toy preferences may reflect both biological activity preferences and social experiences. The researchers used a nonhuman primate group to test whether sex-linked toy interaction patterns could appear without the same human socialisation around toy categories.

Aim and procedure

The researchers observed 34 rhesus monkeys (11 males and 23 females) living in a 135-member troop. Across seven 25-minute trials, one wheeled and one plush toy were made available at the same time; side placement varied across trials. Separate cameras recorded interactions, which observers coded from video using defined behaviour categories. Age and social rank were included in analyses. Human participants were not part of this monkey sample; comparisons with children used data from a separate study.

Results and conclusion

Males showed a stronger preference for wheeled than plush toys. Females interacted with plush toys more than males did, but did not show a statistically reliable preference for either toy type. Preference magnitude differed between the sexes; social rank also related to some female interactions but did not account for the reported sex difference.

A sex difference in interaction with these toy categories appeared in this rhesus group without human-style gendered toy instruction. The findings are consistent with biological influences on activity preferences, but they do not isolate hormones as the cause or show that children’s choices are determined by biology.

Evaluate the evidence

Video records and a behaviour checklist make interactions more systematic; repeated toy presentations and counterbalanced positions reduce a simple side preference explanation.

The focal sample was 34 animals from one established troop; participation and group dynamics limit generalisation to other monkeys or settings.

Toy interaction is an imperfect measure of preference, and the wheeled/plush categories are only approximate counterparts to human toy categories.

The study observes sex differences without experimentally manipulating hormones or social experience; it cannot determine the cause of those differences.

Ethics and issues/debates

The article reports that research followed animal-care guidance and an approved environmental management protocol. The animals remained in their social group; any study with animals still requires welfare review and minimising disruption.

There were no human participants in this monkey sample; do not conflate the separate human comparison data with the animal procedure.

The findings can be discussed in the nature–nurture debate, but ‘not specifically socialised to these toys’ does not mean behaviour developed without social context.

The biological approach highlights possible activity preferences; the observation cannot attribute the pattern to a specific hormone.

The authors note that social processes may shape underlying preferences; biological and social explanations can interact.

Sources for this lesson

Pause and explain

What causal claim does this observation support?

Put the idea to work

Worked example

A student concludes, ‘This experiment proves hormones make boys choose wheeled toys.’ Improve the inference.

Show the worked solution
  1. The observed animals were rhesus monkeys, not boys.
  2. The study recorded toy interactions and found a sex difference, but did not manipulate hormone levels.
  3. The findings are consistent with possible biological influences and leave social and measurement explanations to consider.

Answer The study found that males in one rhesus troop showed a stronger preference for wheeled toys, while females showed more varied choices. It did not test whether hormones caused the pattern in boys or monkeys.

Try a topic test

Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.

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From guided practice to a new situation

Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.

1 · Guided

Summarise the main sex difference and one qualification about the female-monkey result.

Give me a hint

Compare male preference strength with whether the female result was statistically reliable.

Compare my reasoning
  1. Male monkeys showed a stronger preference for wheeled than plush toys.
  2. Females interacted with plush toys more than males but showed no reliable preference between the two types.
  3. The results describe this observed group rather than every rhesus monkey.

Males showed the clearer wheeled-toy preference; female interactions were more variable and did not establish a reliable preference for one category.

Look for these in your work

  • Both sexes described
  • Nonsignificant result kept qualified
  • Sample scope retained
2 · Independent

Evaluate whether the study rules out social explanations of children’s toy preference.

Give me a hint

Consider what the animal sample changes and what it cannot establish about children.

Compare my reasoning
  1. Monkeys are not exposed to the same human toy marketing and gender instructions, so a similar pattern is consistent with biological contributions.
  2. The study did not test children under controlled socialisation conditions or manipulate hormones.
  3. Toy categories and social contexts differ across species, so the result cannot show that children’s preferences are biologically determined.

The monkey findings challenge an exclusively human toy-instruction explanation but do not rule out social influences on children or prove a hormonal cause.

Look for these in your work

  • Animal result applied cautiously
  • Unmanipulated causes recognised
  • Cross-species limit explained
3 · Transfer

Design a follow-up that tests whether the recorded pattern changes with toy availability while protecting animal welfare.

Give me a hint

State a behavioural measure, a comparison and an ethical safeguard.

Compare my reasoning
  1. Use a non-invasive observation plan approved by an animal-care committee and keep animals with their established group.
  2. Counterbalance toy side and record time or frequency of defined interactions with each toy type.
  3. Replicate across more than one troop and avoid restricting food, social contact or normal movement to create a choice.

A welfare-reviewed, non-invasive multi-group observation with a consistent coding rule and counterbalanced placement could test whether the pattern repeats.

Look for these in your work

  • Measure is observable
  • A fair presentation is specified
  • Welfare and replication addressed

Common mistakes

  • Saying all female monkeys preferred plush toys
  • Calling the animal sample human participants
  • Treating absence of human-style toy socialisation as absence of all social influences
  • Claiming hormones were experimentally manipulated
Recall without your notes

What can you explain now?

What result best describes the female monkeys?

Compare with the explanation

They showed more varied preferences and no reliable preference for one toy type

This avoids turning a nonsignificant tendency into a firm group preference.

After trying it yourself, choose your next review. This is your self-assessment.

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Make it stick

Name the aim, the best-evidenced result and one methodological limitation of Hassett et al..

If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.

Keep learning Psychology

Course scope and assessment

Seven original lessons map all 15 AS research-method and methodological-concept sections to explained Guided, Independent and Transfer practice. All 12 compulsory AS core studies have original study-specific teaching and staged practice; five additional A Level methodology lessons cover research design and validity. All 15 Clinical, all 15 Consumer (2.1.1–2.5.3) and all 15 Health (3.1.1–3.5.3) Psychology sections link to original teaching and staged practice. All 15 Organisational Psychology sections 4.1–4.5 now have original teaching and explained staged practice; the six new 4.4–4.5 lessons bring the planning map to 92 of 92 indexed sections. Consumer lessons cover physical and psychological environments; decision models, heuristics and mistakes; packaging, selling and buying; advertising, self-monitoring, product placement, brand recognition and slogans. Evaluation boundaries are explicit: studies use particular products, samples, tasks and settings; gaze, recall, self-report, EEG indices, ratings, choices and purchases are different outcomes. Health evidence is bounded: Laba et al. measured hypothetical preferences; Riekert and Drotar raise a non-response concern; Chung and Naya's cap tracked openings, not swallowing; Chaney et al. was a short caregiver-reported pilot; Yokley and Glenwick examined immunisation attendance in one public-health setting. MacLachlan et al. report one patient, not a controlled treatment effect; Brudvik et al. compared separate child, parent and physician ratings in one emergency department. Chandola et al. found a cohort association; Wang et al. measured responses during a monitored arithmetic task; Evans and Wener observed commuters; Bridge et al. found mixed self-rated outcomes in radiotherapy. Janis and Feshbach measured short-term self-reports in one school; Lewin et al. tested a rehabilitation package, not information alone. Tapper et al. and Fox et al. studied bounded school and worksite programmes; incentive effects do not establish transfer or rule out reporting effects. Weinstein measured comparative expectations, while Seligman’s framework is conceptual and Shoshani and Steinmetz used a school-level comparison. These findings do not establish universal health effects or diagnose individuals. Need-theory examples use a child measurement study, not a workplace test; SMART is a practical checklist, not a motivational theory. Landry et al. compared reward framing with student volunteers in a lab; this does not establish universal effects in workplaces. Cuadrado et al. (2008) measured undergraduate evaluations of presented leaders, not workplace performance or hiring; this does not establish a universal gender effect. The historical 1995 Munchausen criteria are not a current diagnostic checklist. Cambridge’s 2028–2030 Reference List treats Oruč et al. (1997) as an example of genetic explanation although its participants had bipolar I; gambling disorder is listed in Cambridge’s Clinical topic but classified under addictive behaviours in ICD-11. Candidates choose two options, but all four remain listed so schools can select a route. The 92-section count is a planning index, not a Cambridge score. Remaining work is deeper coverage review, separate-year syllabus reconciliation, timed-paper practice and human subject-expert review. The separate 2027 and 2024–2026 syllabuses are not reconciled into this route. Practice is not official grading, a timed-paper simulation or human subject-expert review.

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